This invention relates to a laser machining device for machining an object or workpiece by a laser beam and, more particularly, to a pattern transfer device for use typically in either a laser marker or a pattern generator.
Various laser machining devices are known. An example is disclosed in U.S. Pat. No. 4,734,558 issued to Masakazu Nakano and assigned to NEC Corporation, Japan, the present assignee. Another example is revealed in U.S. patent application Ser. No. 590,837 filed Oct. 1, 1990, by Koji Wakabayashi for assignment to the instant assignee based on a patent application filed in Japan under Patent Application No. 254,126 of 1989. Still another example will later be described. When used to machine or treat the object, the laser beam is herein called a machining laser beam.
According to the above-cited Nakano patent, a laser machining device comprises a machining laser oscillator which generates a machining laser beam along a machining laser beam axis when excited. A table or worktable is for carrying the object and for controllably moving the object relative to the machining laser beam axis. A liquid crystal display (LCD) is for displaying a position reference pattern which is typically an on-off or transparent-opaque pattern and provides a machining pattern on the object. The machining laser beam machines the objects in accordance with the machining pattern.
According to the above-referenced Wakabayashi patent application, a laser machining device comprises a machining laser beam source which generates a machining laser beam along a machining laser beam axis when a machining laser oscillator is placed therein and excited. A table is for carrying the object and is controllably subjected to displacement or movement relative to the machining laser beam axis. A data signal producing unit is coupled to the table and is for producing, in response to the relative displacement of the table, data signals collectively representative of a machining pattern. An acousto-optic modulator unit is placed along the machining beam axis and is for modulating the machining laser beam in compliance with the data signals to make the machining laser beam machine the object in accordance with the machining pattern.
An excellent Q switch is disclosed in U.S. Pat. No. 3,437,073 issued to John F. Forkner. In the laser machining device according to Wakabayashi, two such Q switches are preferably used in the acousto-optic modulator unit. In addition, such a Q switch is more preferably used additionally in the machining laser beam source to on-off control the machining laser beam. In this event, the machining laser beam source is for controllably generating the machining laser beam.
The laser machining device of Wakabayashi is of an acousto-optic modulator type. Generally speaking, a laser machining device of the acousto-optic modulator type is operable at a high machining speed.
The laser machining device of Nakano is of a liquid crystal display mask transfer type. A conventional laser machining device of the liquid crystal display mask transfer type is advantageous in that it is possible to vary the shape of the position reference pattern as desired. The fact should, however, be noted that the machining laser beam is directly incident on the liquid crystal display. The machining laser beam mast have a wavelength range compatible with the liquid crystal display. In addition, the machining laser beam must have a weak energy density on the liquid crystal display so as not to damage the liquid crystal display. This results in a low machining speed.